diatom — noun Etymology: ultimately from Greek diatomos cut in half, from diatemnein to cut through, from dia + temnein to cut more at tome Date: 1845 any of a class (Bacillariophyceae) of minute planktonic unicellular or colonial algae with silicified… … New Collegiate Dictionary

diatom — Algae of the division Bacillariophyta; largely unicellular and characterized by having cell walls of hydrated silica embedded in an organic matrix. The cell walls are formed in two halves that fit together like the lid and base of a pillbox and… … Dictionary of molecular biology